The present invention relates to a concentrate which contains a biocide and is primarily solid under ambient conditions. By primarily solid is meant solid, wax-like or having another non-gas and non-liquid appearance, such as a gel or paste composition.
Polymer compositions are protected against fungal or bacterial attack by the incorporation therein of a microbiocide to prevent deterioration of the polymer composition due to microbiological attack on the susceptible portion of its components. For example, German Patent DE 1,288,790 discloses the incorporation of urea or thiourea compounds, optionally together with a plasticizer, into polymers to impart antimicrobiocidal properties to the polymers. Furthermore, U.S. Pat. No. 3,864,468 discloses the incorporation of microbiocides, such as 10,10'-oxybisphenoxyarsine (OBPA), into plastisols which may comprise liquid plasticizers, such as dioctylphthalate.
In order for the microbiocide to be effective in the polymer composition, it is necessary that it be compatible therewith and uniformly dispersable therein to avoid the formation of areas within the polymer which contain insufficient biocide to prevent polymer deterioration.
To avoid toxicological problems related to the handling of the pure microbiocide, microbiocides are presently added to polymer compositions as a microbiocide-containing concentrate. Said concentrate can take different forms, such as: a liquid, a powder, or a non-powdery solid.
Liquid concentrates are usually based on a plasticizer which is liquid at ambient conditions in combination with a cosolvent. By ambient conditions is meant: standard pressure and room temperature (about 20.degree.-30.degree. C.). Without a cosolvent only low concentrations of the microbiocide can be obtained due to the low solubility of commonly used microbiocides in liquid plasticizers. Said cosolvent, however, may destabilize the concentrate or adversely effect the polymer composition with which it is to be mixed. A further problem arises from the fact that it is difficult to completely remove a liquid concentrate from packaging used for transport or storage, so that unless it can be reused or cleaned, this packaging becomes toxic waste.
Problems related to the toxicity of such compositions can be overcome by incorporating the microbiocide in a solid composition in such a way that it is immobilised under conditions that allow transport, storage, and the like. The following two ways of doing this were developed in the past.
U.S. Pat. No. 4,086,297 describes a method of making a concentrate to be incorporated into a second, polymeric composition, which concentrate comprises a homogeneous, melt-blended mixture of a biocide and at least 24 wt. % of a solid thermoplastic resin. This concentrate, however, cannot be added successfully to a plastisol because of its relatively high melting point and low solubility therein.
U.S. Pat. No. 4,663,359 describes a method of making a powdery concentrate in which a microbiocide is absorbed on a porous resin powder. Said concentrate is said to be mixable with a plastisol, however, it has been found that such dry blends are not universally compatible with pastisols. In other words, it is necessary to prepare various different types of dry blends in order to obtain the desired compatibility with plastisols. A plastisol can, therefor, only be adequately protected against fungal or bacterial attack if more of the concentrate is added than would be needed in case of a homogeneous distribution, thereby increasing the toxicity of the plastisol. Accordingly, a need exits for a microbiocide concentrate which can be used to make a homogeneous distribution of a microbiocide in a plastisol.
Further, the powdery concentrate is also susceptible to the formation of fines which may lead to a dust hazard. Thus, there is also a need for a solid masterbatch formulation which is not susceptible to the formation of fines. These and other objects of the invention will be apparent to one of oridinary skill in the art from the summary and detailed description which follow.